Question
hy might we want to use an electromagnet rather than a permanent bar magnet? There are two obvious advantages to using electromagnets.
Firstly they can be switched on and off. Complete an electric circuit and a current passes to produce a magnetic field. Switch off the current and the magnetism disappears (provided the iron forms a temporary magnet).
Also, their magnetic strength can be changed. The strength of the magnetic field around the solenoid can be increased by:
Increasing the number of coils (or turns) of wire.
Increasing the electric current through the coil.
Placing a magnetic material inside the solenoid coil.
Car scrap-yards use huge electromagnets to lift heaps of crumpled iron and steel. Switch off the current and the object crashes to the ground.
In the home, by far the most common use of electromagnets is in electric motors. Think of all of those bits of electrical equipment with some kind of electric motor: vacuum cleaners, refrigerators, washing machines, tumble driers, food blenders, fan ovens, microwaves, dish-washers, hair driers.
The list is a long one, and when you start thinking more widely about electric motors in cars, lawn-mowers and a whole host of industrial applications, it becomes obvious that this application of electromagnets is extensive and extremely important to our daily lives. The question of how electric motors work builds on the basics of magnetism introduced here, and is usually worked on in later years.
Bells, relays and motors
Electromagnetic door bells are make and break devices which work via an electromagnet. There is one electric circuit containing two switches. One is a conventional push-button switch. The second has two parts, a spring and an electromagnet. The alternating action of the spring and the electromagnet makes and breaks the circuit for as long as the push-button switch is pressed.
An electromagnetic relay consists of two circuits. The first circuit contains a simple electromagnet which requires a relatively small current to make it work. When the switch is closed, there is an electric current through the coil of wire and the iron rocker arm is attracted to the electromagnet. The arm rotates about the pivot and closes a switch to complete the second circuit and the motor starts up – the motor requires a much larger current. When the switch in the first circuit is opened the electromagnet releases the rocker arm and the switch springs open again. The motor circuit is now broken.
The motor is more complex than either, but included here for completeness.
**Be sure to answer both questions**
2. Why are electromagnets preferred in the real world over permanent magnets?
Firstly they can be switched on and off. Complete an electric circuit and a current passes to produce a magnetic field. Switch off the current and the magnetism disappears (provided the iron forms a temporary magnet).
Also, their magnetic strength can be changed. The strength of the magnetic field around the solenoid can be increased by:
Increasing the number of coils (or turns) of wire.
Increasing the electric current through the coil.
Placing a magnetic material inside the solenoid coil.
Car scrap-yards use huge electromagnets to lift heaps of crumpled iron and steel. Switch off the current and the object crashes to the ground.
In the home, by far the most common use of electromagnets is in electric motors. Think of all of those bits of electrical equipment with some kind of electric motor: vacuum cleaners, refrigerators, washing machines, tumble driers, food blenders, fan ovens, microwaves, dish-washers, hair driers.
The list is a long one, and when you start thinking more widely about electric motors in cars, lawn-mowers and a whole host of industrial applications, it becomes obvious that this application of electromagnets is extensive and extremely important to our daily lives. The question of how electric motors work builds on the basics of magnetism introduced here, and is usually worked on in later years.
Bells, relays and motors
Electromagnetic door bells are make and break devices which work via an electromagnet. There is one electric circuit containing two switches. One is a conventional push-button switch. The second has two parts, a spring and an electromagnet. The alternating action of the spring and the electromagnet makes and breaks the circuit for as long as the push-button switch is pressed.
An electromagnetic relay consists of two circuits. The first circuit contains a simple electromagnet which requires a relatively small current to make it work. When the switch is closed, there is an electric current through the coil of wire and the iron rocker arm is attracted to the electromagnet. The arm rotates about the pivot and closes a switch to complete the second circuit and the motor starts up – the motor requires a much larger current. When the switch in the first circuit is opened the electromagnet releases the rocker arm and the switch springs open again. The motor circuit is now broken.
The motor is more complex than either, but included here for completeness.
**Be sure to answer both questions**
2. Why are electromagnets preferred in the real world over permanent magnets?
Answers
GPT-4o mini
Electromagnets are often preferred over permanent magnets in various applications due to several significant advantages:
1. **Control Over Magnetism**: Electromagnets can be easily switched on and off by controlling the electric current flowing through the coil. This allows for precise control over the magnetic field's presence, which is particularly important in applications where the magnetism needs to be engaged and disengaged, such as in electric motors, doorbells, and various control systems.
2. **Variable Strength**: The magnetic field strength of an electromagnet can be adjusted by modifying several factors:
- **Number of Coils**: Increasing the number of turns of wire around the core enhances the magnetic field strength.
- **Electric Current**: Increasing the electric current flowing through the wire also increases the magnetic field intensity.
- **Core Material**: Inserting a ferromagnetic material (such as iron) into the coil further amplifies the magnetic field.
This versatility allows for applications where different levels of magnetic strength are required, making electromagnets highly adaptable.
3. **Size and Weight**: In many cases, electromagnets can be designed to be smaller and lighter than equivalent permanent magnets, especially for applications requiring high magnetic fields. This is particularly useful in applications like motors and magnetic cranes, where space and weight are critical factors.
4. **Diminished Demagnetization**: Permanent magnets can lose their magnetism over time due to temperature fluctuations, physical shocks, or other environmental factors. Electromagnets do not have this limitation, as their magnetic field is created by the flow of electricity, and can be reset instantly when needed.
5. **High Efficiency in Energy Transfer**: In electric motors and generators, electromagnets facilitate the conversion between electrical energy and mechanical energy. They efficiently create rotating magnetic fields that drive motion, making them essential for a wide range of electromechanical systems.
In summary, the ability to control and adjust the magnetic properties of electromagnets makes them invaluable in numerous practical applications compared to permanent magnets.
1. **Control Over Magnetism**: Electromagnets can be easily switched on and off by controlling the electric current flowing through the coil. This allows for precise control over the magnetic field's presence, which is particularly important in applications where the magnetism needs to be engaged and disengaged, such as in electric motors, doorbells, and various control systems.
2. **Variable Strength**: The magnetic field strength of an electromagnet can be adjusted by modifying several factors:
- **Number of Coils**: Increasing the number of turns of wire around the core enhances the magnetic field strength.
- **Electric Current**: Increasing the electric current flowing through the wire also increases the magnetic field intensity.
- **Core Material**: Inserting a ferromagnetic material (such as iron) into the coil further amplifies the magnetic field.
This versatility allows for applications where different levels of magnetic strength are required, making electromagnets highly adaptable.
3. **Size and Weight**: In many cases, electromagnets can be designed to be smaller and lighter than equivalent permanent magnets, especially for applications requiring high magnetic fields. This is particularly useful in applications like motors and magnetic cranes, where space and weight are critical factors.
4. **Diminished Demagnetization**: Permanent magnets can lose their magnetism over time due to temperature fluctuations, physical shocks, or other environmental factors. Electromagnets do not have this limitation, as their magnetic field is created by the flow of electricity, and can be reset instantly when needed.
5. **High Efficiency in Energy Transfer**: In electric motors and generators, electromagnets facilitate the conversion between electrical energy and mechanical energy. They efficiently create rotating magnetic fields that drive motion, making them essential for a wide range of electromechanical systems.
In summary, the ability to control and adjust the magnetic properties of electromagnets makes them invaluable in numerous practical applications compared to permanent magnets.